Generally around the world, industrial power consumption accounts for 40-60% of a nation's total energy consumption, and 70% of the industrial power is used by motors. Accordingly, motors consume nearly 50% of a nation's power supply. If motor efficiency can be raised by 1-2%, it will greatly help reduce energy consumption and carbon emissions. Therefore, promotion of high-efficiency motors has become an important task.
It is without question that motors are the commonest and most convenient source of driving force and thus are widely adopted in various mechanical rotating devices for industrial, commercial and home applications. Due to the wide adoption, the total energy consumption used by motors takes up half of a nation's power supply, so how to raise motor energy efficiency is of grave importance.
Under the circumstances, the U.S. Energy Independence and Security Act of 2007(EISA 2007), in effect since December 2010, requires that manufacturers produce high-efficiency motors compliant with the National Electrical Manufacturers Association's (NEMA) premium efficiency (equivalent to IE3). Furthermore, the regions applying the International Electrotechnical Commission (IEC) standard including Europe and Japan will start to implement the IE3 standard from 2015 in succession. It is obvious that high-efficiency motors have become a prevailing trend worldwide.
"We have been devoted to the R&D and manufacture of high-efficiency motors for over a decade. Our high-efficiency motors complied with the U.S. EPAct Energy Efficient Level (equivalent to IE2) as early as 1997. Closely following the EISA regulations effective later on, we continue to offer a full lineup of NEMA Premium 1-200Hp motors," indicated Hank Y.H. Wu, General Manager, Motor Design Division, Motor Business Unit, TATUNG Power Business Group.
Varying standards across different regions challenge suppliers' technological capabilities
Judging from past export experience, Wu pointed out each country has different regulations about motors. To provide IE3 premium-efficiency motors compliant with vastly different requirements around the world is a challenge to suppliers' capabilities in terms of finding a balance among production, design and materials.
Take the U.S. for example. Although it leads the world in high-efficiency motor implementation schedule, the NEMA standard has no limitation on motor frame sizes. That is, the horsepower rating and number of poles is not strictly related to the frame size, so suppliers have more flexibility in production and can meet the high-efficiency requirements by properly elongating iron cores and adding copper conductors.
However, Japan's JIS and Taiwan's CNS standards previously set a direct bond between the horsepower rating and number of poles and the frame size. In other words, a certain rating and number of poles had to correspond to a fixed frame size, meaning the external mounting dimensions were fixed. These standards have been long adopted and followed by users in the regions. As a result, when the new IE2 or IE3 standard replaces older specifications, new motors, despite their higher efficiency, still have to follow old requirements on external dimensions for customer substitution convenience. Furthermore, Japan has a demand to satisfy different voltage and frequency application (200V/220V, 50Hz/60Hz), posing additional difficulty for motors to meet the IE3 standard. As such, more sophisticated technologies, other than just adding copper conductors and elongating iron cores, are needed to overcome these limitations. Therefore, to produce IE3 premium-efficiency motors meeting Japan and Taiwan requirements is a challenge in terms of both costs and technology, indicated Wu.
In search of a breakthrough to enhance efficiency through design and material improvement
Wu explained the internal structure of a motor is actually quite simple, made up of a stator and a rotor formed by stacking silicon steel sheets comprising an iron core. The stator and rotor has multiple slots for copper or aluminum conductors to pass through. Electromagnetic loss resulted from electric current and magnetic flux passing through the conductors and the iron core is the main source of motor energy loss. Therefore, adding copper conductors and elongating the iron core is a basic way to reduce loss and raise efficiency. In addition to adding copper and iron, other methods to reduce mechanical loss and stray loss should also be considered. For example, mechanical loss due to friction resulted from rotation of bearings or fans can be reduced by optimizing bearing selection, fan design and airflow circulation, thereby enhancing heat dissipation and fan efficiency. In terms of electrical engineering, a matching design of the slot shape and slot number and the number of winding turns are areas with room for improvement. However, Wu pointed out the efficiency improvement generated from simply making design improvements in electrical or mechanical engineering or even from selecting higher grade iron core materials can hardly compare to the effects achieved by adding copper and iron. All factors have to be considered to strike a balance that creates optimum effects.
The Taiwan government has planned to implement IE3 from July 1, 2016, but Tatung is a step ahead and had already launched IE3 premium-efficiency motors suitable for the Taiwan market in June 2014. Tatung keeps working on striking a balance between design optimization as well as material selection and making improvements and breakthroughs on details including frame fin shapes, casing thickness, fan construction, and slot shape design. Advanced products are scheduled to enter the market by 2016.
Wu reiterated although high-efficiency motors have higher prices, which may deter users from making purchases, they actually have a long operation life of 10-20 years. From the perspective of product lifetime, the purchase costs are insignificant as electricity expenses take up a large proportion of operation costs. Accordingly, users may pay slightly higher to purchase a high-efficiency motor, but the savings on electricity expenses during operation will compensate for and be far beyond the purchase costs. Therefore, high-efficiency motors are a smart and valuable investment.
Hank Y.H. Wu, General Manager, Motor Design Division, Motor Business Unit, TATUNG Power Business Group
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